SACRAMENTO, Calif., April 7 (Reuters) - The battle over a proposed ban in California on using killer whales in entertainment shows at amusement parks like SeaWorld stepped up on Monday, as animal rights activists converged on Sacramento to present petitions they said were signed by 1.2 million people worldwide.

The symbolic move to present the petitions by representatives of the Animal Welfare Institute and others came a day before a committee of state lawmakers was set to debate a bill to end orca shows at SeaWorld's San Diego park.

The lobbying by supporters comes days after executives at SeaWorld spent two days at the state capitol presenting their case.

The bill to ban orca shows was introduced by state Assemblyman Richard Bloom, a Santa Monica Democrat, who has said he was inspired by the documentary film, "Blackfish," which tells the story of an orca that killed a trainer at SeaWorld's park in Orlando, Florida, in 2010.

The bill would ban using the majestic black-and-white mammals in shows, a mainstay of the SeaWorld parks, and would also outlaw domestic breeding of the whales.

"SeaWorld is already mounting a vicious campaign to defeat this assemblyman's brave move," the advocacy group Sum of Us declared on its website, urging followers to sign the petitions.

"Blackfish," which supporters planned to screen near the capitol in Sacramento later on Monday, shows what supporters say is ill treatment of the animals at SeaWorld parks, including the separation of young orcas from their mothers despite the animals' social and matriarchal nature.

"The film got wide distribution so we are not surprised that people were misled by the falsehoods and tricks in the movie," said John Reilly, president of SeaWorld's San Diego park. "It's understandable that many people would sign a petition on the premise of the movie. We know that when they learn the facts, people support SeaWorld."

Reilly told lawmakers last week that the accusations were untrue. He said the filmmakers exaggerated a claim that animals were separated from their mothers by using footage of a baby orca while discussing the removal of a much older animal from the group because it had been disruptive.

He also said the company does not capture wild orcas for use in its shows, and has not for 30 years. SeaWorld also runs a multimillion-dollar animal rescue program and funds many avenues of marine science research, he added.

"This film was a piece of propaganda and an attempt to exploit a tragic incident," Reilly said.

RETHINKING ORCA SHOWS

Naomi Rose, an orca biologist with the Animal Welfare Institute who served as an adviser to the film, said that although other states have implemented bans on orca shows, California would be the first state that actually has such entertainment to do so.

"I've been waiting for 20 years for someone like Mr. Bloom to come along and do something about this," said Rose, who believes that the shows, which feature orcas jumping through hoops of fire and performing other tricks, are inhumane.

Many consumers are rethinking the company's use of marine mammal parks in the wake of the film, which came out last year.

But SeaWorld has been a part of the San Diego region's economy for decades, providing jobs and serving as the No. 1 paid tourist attraction in the area.

The bill is opposed by a Republican state assemblyman who represents part of the San Diego area. Moreover, the incoming speaker of the state assembly, Toni Atkins, is a longtime supporter of the park, and recently spoke at its 50th anniversary celebration.

Atkins, a Democrat, has refrained from saying whether she will support the bill. But she stressed the importance of the park to the region in a statement sent to Reuters by her spokeswoman.

"In my many years of experience with the folks at SeaWorld, everyone I have met there has had a deep concern and affection for the animals in their care," Atkins said. "When a sea animal needs care, San Diegans immediately think of SeaWorld." (Reporting by Sharon Bernstein, editing by Cynthia Johnston and G Crosse)